Up to now, a disc cartridge holding a disc-shaped recording medium such as a magnetic disc or a magneto-optical disc, has been in extensive use. This sort of the disc cartridge includes a main cartridge body portion combined from an upper cartridge half and a lower cartridge half. The disc-shaped recording medium is rotatably housed in a disc housing section provided in the interior of the main cartridge body portion.
In the upper and lower surfaces of the main cartridge body portion accommodating the disc-shaped recording medium are formed facing recording and/or reproducing apertures for partially exposing the signal recording area of the disc-shaped recording medium housed in the disc housing section across the inner and outer rims of the disc to outside and for permitting intrusion of recording/reproducing means provided on the recording/reproducing apparatus. The recording/reproducing apertures are opened and closed by a shutter member provided for movement on the main cartridge body portion.
The lower cartridge half constituting the lower surface of the main cartridge body portion is provided with a center opening at a mid portion of the disc housing section for permitting intrusion of a turntable on the recording/reproducing apparatus therein. This center opening causes a center hub provided at the center of the disc-shaped recording medium housed within the main cartridge body portion to be exposed to the lower surface side of the main cartridge body portion. The disc-shaped recording medium housed in the main cartridge body portion has its center hub clamped by the turntable intruded via the center opening in the main cartridge body portion so that the disc-shaped recording medium is rotated in unison with the turntable.
If the disc cartridge, configured as described above, is loaded on the recording/reproducing apparatus, the shutter member is moved to open the recording/reproducing apertures via which the recording/reproducing means of the recording/reproducing apparatus is intruded into the interior of the main cartridge body portion. The recording/reproducing means is moved across the inner and outer rims of the signal recording area of the disc-shaped recording medium in order to scan the signal recording area of the disc-shaped recording medium for recording/reproducing information signals.
Meanwhile, with recent tendency to multi-media, the information signals handled, such as video or audio data, are diversified and increased in volume. Moreover, the recording capacity of the disc cartridge is increasing. For recording the information signals of a large volume, there has been proposed a disc cartridge having information signals recorded thereon to higher recording density.
On the other hand, it is also proposed to use an outer rim portion of the disc-shaped recording medium as a signal recording area, not used thus far to this end, with a view to increasing the recording capacity of the information signals even although the disc-shaped recording medium of the same size as the conventional disc-shaped recording medium is held in the main cartridge body portion of the same size and shape as the conventional main cartridge body portion.